In the field of oxide-supported catalysts, in general, and especially for olefin polymerization catalysts, it is often desired to remove surface hydroxyl groups from the oxide support particles before and/or during manufacture of the supported catalyst.
In the past, various thermal and/or chemical treatments have been used in an effort to achieve dehydroxylation of the oxide particles.
Thermal treatments (i.e. calcining) are advantageous from the point that they do not add undesirable chemicals to the support and that they are relatively simple inexpensive processes. Unfortunately, thermal treatments are often ineffective for achieving a high degree of dehydroxylation. Further, for many porous oxide supports (e.g., silica gel), thermal treatments often result in an undesirable loss of pore volume, shrinkage of the pores and/or loss of surface area.
A variety of chemical treatments have been attempted. Many types of chemicals have been used such as organo aluminum compounds, magnesium chloride/dehydrating agent combinations, organosilanes, halosilanes, silazanes, etc. These various chemical processes are often expensive and may result in the addition of undesired or complicating constituents to the oxide support.
Thus, there remains a need for improved techniques for dehydroxylation and improved dehydroxylated supports.